All-optical clock recovery of 20 Gbit/s NRZ-DPSK signals using polarization-maintaining fiber loop mirror filter and semiconductor optical amplifier fiber ring laser

All-optical clock recovery (CR) from 20 Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signals are demonstrated experimentally by using a polarization-maintaining fiber loop mirror filter (PMF-LMF) and a semiconductor optical amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signals were conveniently and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signals are injected into the SOA fiber laser for CR. The recovered clock signals is with the extinction ratio (ER) of 10 dB and the root-mean-square (RMS) timing jitter of 750 fs in 2³¹ − 1 long pseudorandom binary sequence (PRBS) NRZ-DPSK signals measurement. Moreover, the broad wavelength tunability of recovered clock stemmed from the use of SOAs as modulator and the gain medium are shown too.